Rainer Schoedel, Antxon Alberdi, Izaskun Jimenez-Serra, Farhad Yusef-Zadeh, Angela Gardini, Michael Kramer, Miguel Perez Torres, Mark R. Morris, Jan Forbrich, A… 展开作者
Rainer Schoedel, Antxon Alberdi, Izaskun Jimenez-Serra, Farhad Yusef-Zadeh, Angela Gardini, Michael Kramer, Miguel Perez Torres, Mark R. Morris, Jan Forbrich, Adriano Ingallinera, Francisco Nogueras-Lara, Jonathan D. Henshaw, Steven N. Longmore, Javier Moldon, Ian Heywood, Isabella Rammala, Farideh Mazoochi, Fatemeh Tabatabei, Lourdes Verdes Montenegro, Susana Sanchez Exposito
凭借其极高的恒星和恒星残骸密度、致密的年轻大质量星团、高比恒星形成率、强辐射场、高磁场强度，以及类似于高红移星系和星暴的星际介质性质，银河系中心是我们能够详细观测的最极端环境。它也是我们能够以仅几毫秒差距的分辨率观测到的唯一星系核。这使其成为理解星系核物理、恒星形成以及两者之间联系的关键目标。它使得在明确距离下研究大量原本罕见的恒星（如极大质量恒星和恒星残骸）成为可能，从而有助于解释它们的性质。银河系中心一直并正在利用最先进的设施进行深入研究。在这份白皮书中，我们主张利用平方公里阵列（Square Kilometre Array, SKA）对以大质量黑洞人马座A*（Sagittarius A*）为中心、约1.25x0.3平方度（180x40 pc**2）的区域进行大面积、多波长巡天，并在十年内对核星团进行重复深度观测，这将使科学界能够利用单一数据集解决多个科学问题。
英文摘要：
With its extreme density of stars and stellar remnants, dense young massive clusters, high specific star formation rate, intense radiation field, high magnetic field strength, and properties of the interstellar medium that resemble those in high redshift galaxies and starbursts, the Galactic Centre is the most extreme environment that we can observe in detail. It is also the only nucleus of a galaxy that we can observe with a resolution of just a few milli parsecs. This makes it a crucial target to understand the physics of galactic nuclei and star formation, as well as the connection between them. It enables studies of a large number of otherwise rare objects, such as extremely massive stars and stellar remnants, at a well-defined distance, thus facilitating the interpretation of their properties. The Galactic Centre has been and is being studied intensively with the most advanced facilities. In this White Paper, we advocate for a large-area, multi-wavelength survey with the Square Kilometre Array of an area of about 1.25x0.3 deg**2 (180x40 pc**2), centered on the massive black hole Sagittarius A* and for repeated deep observations of the nuclear star cluster over a decade, which will allow the community to address multiple science problems with a single data set.
This white book stems from the contributions presented at the Portuguese SKA Days, held on the 6th and 7th February 2018 with the presence of the SKA Deputy Director General Alistair McPherson and the SKA Science Director Robert Braun. This initiative was held to promote the Square Kilometer Array (SKA) - the world's largest radio telescope - among the Portuguese scientific and business communities with support from the Portuguese Science and Technology Foundation (FCT) with the contribution of Portuguese policy makers and researchers. The meeting was very successful in providing a detailed ov…
The Nearest Galactic Nucleus: Studying the Galactic Centre with SKA-Mid
Northwestern University（西北大学）；Max-Planck-Institute for Radio Astronomy（马克斯·普朗克射电天文研究所）；University of California Los Angeles（加州大学洛杉矶分校）；University of Oxford（牛津大学）；University of Hertfordshire（赫特福德大学）；Astrophysics Research Institute, Liverpool John Moores University（利物浦约翰摩尔斯大学天体物理研究所）；Cosmic Origins Of Life (COOL) Research DAO（宇宙生命起源（COOL）研究去中心化自治组织）；Rhodes University（罗德岛大学）；Institute for Research in Fundamental Sciences (IPM)（基础科学研究所）；Tata Institute of Fundamental Research（塔塔基础研究所）；Masaryk University（马萨里克大学）；Charles University（查理大学）
The Engineering Development Array (EDA) is a single test station for Square Kilometre Array (SKA) precursor technology. We have used the EDA to detect low-frequency radio recombination lines (RRLs) from the Galactic Centre region. Low-frequency RRLs are an area of interest for future low-frequency SKA work as these lines provide important information on the physical properties of the cold neutral medium. In this project we investigate the EDA, its bandpass and the radio frequency interference environment for low-frequency spectroscopy. We present line spectra from 30 to 325 MHz for the Galacti…
Future observations with next generation radio telescopes will help us to understand the presence and the evolution of magnetic fields in galaxy clusters through the determination of the so-called Rotation Measure (RM). In this work, we applied the RM-synthesis technique on synthetic SKA1-MID radio images of a pair of merging galaxy clusters, measured between 950 and 1750 MHz with a resolution of 10 arcsec and a thermal noise of 0.1$μ$Jy/beam. The results of our RM-synthesis analysis are compared to the simulations' input parameters. We study two cases: one with radio haloes at the cluster cen…
The high stellar density in the central parsecs around the Galactic Centre makes it a seemingly favourable environment for finding relativistic binary pulsars. These include pulsars orbiting other neutron stars, stellar-mass black holes or the central supermassive black hole, Sagittarius A*. Here we present multi-epoch pulsar searches of the Galactic Centre at four observing frequencies, (4.85, 8.35, 14.6 18.95) GHz, using the Effelsberg 100-m radio telescope. Observations were conducted one year prior to the discovery of, and during monitoring observations of, the Galactic Centre magnetar PSR…
We searched through the entire Gaia EDR3 candidate white dwarf catalogue for stars with proper motions and positions that are consistent with the stars having escaped from the Alpha Persei cluster within the past 81~Myr, the age of the cluster. In this search we found five candidate white dwarf escapees from Alpha Persei and obtained spectra for all five. We confirm that three are massive white dwarfs sufficiently young to have originated in the cluster. All three are more massive than any white dwarf previously associated with a cluster using Gaia astrometry, and possess some of the most mass…
The Gaia catalogue of nearby stars (GCNS) divided all objects with parallaxes $>$10mas into GCNS-selected and GCNS-rejected 100pc samples. Below the white dwarf (WD) sequence in the complete GCNS color-magnitude diagram (CMD), at $Gabs>14.7+4.7(G-RP)$, there appear 60 GCNS-selected faint blue white dwarfs (FBWDs). However this CMD region is also populated by 411 GCNS-rejected objects, mainly from crowded regions towards the Galactic centre and the Magellanic Clouds. The WD catalog of Gentile Fusillo et al. (2021) lists only 47 GCNS-selected but also 8 GCNS-rejected objects. I confirm 59 of the…
Discovery of a double white dwarf in the Galactic globular cluster NGC 6397
Georg-August-Universität Göttingen（哥廷根大学）；Friedrich-Alexander University Erlangen-Nuremberg（埃尔朗根-纽伦堡大学）；Liverpool John Moores University（利物浦约翰摩尔斯大学）；University of California, San Diego（加州大学圣地亚哥分校）
The SKA PAthfinder Radio Continuum Surveys (SPARCS) are providing deep-field imaging of the faint (sub-mJy) extra-galactic radio source populations through a series of reference surveys. One of the key science goals for SPARCS is to characterize the relative contribution of radio emission associated with AGN from star-formation (SF) in these faint radio source populations, using a combination of high sensitivity and high angular resolution imaging over a range of spatial scales (arcsec to mas). To isolate AGN contribution from SF, we hypothesise that there exists a brightness temperature cut-o…
A large sample of white dwarfs is selected by both proper motion and colours from the Pan-STARRS 1 3π Steradian Survey Processing Version 2 to construct the White Dwarf Luminosity Functions of the discs and halo in the solar neighbourhood. Four-parameter astrometric solutions were recomputed from the epoch data. The generalised maximum volume method is then used to calculate the density of the populations. After removal of crowded areas near the Galactic plane and centre, the final sky area used by this work is 7.833 sr, which is 83% of the 3π sky and 62% of the whole sky. By dividing the sky …
We search through an eight-million cubic-parsec volume surrounding the Pleiades star cluster and the Sun to identify both the current and past members of the Pleiades cluster within the Gaia EDR3 dataset. We find nearly 1,300 current cluster members and 289 former cluster candidates. Many of these candidates lie well in front or behind the cluster from our point of view, so formerly they were considered cluster members, but their parallaxes put them more than 10 pc from the centre of the cluster today. Over the past 100 Myr we estimate that the cluster has lost twenty percent of its mass inclu…
Current observations of the Galactic Center (GC) seem to display a core-like distribution of bright stars from $\sim 5"$ inwards. On the other hand, we observe young, massive stars at the GC, with roughly 20-50\% of them in a disc, mostly in the region where the bright giants appear to be lacking. In a previous publication we put the idea forward that the missing stars are deeply connected to the presence of this disc. The progenitor of the stellar disc is very likely to have been a gaseous disc that at some point fragmented and triggered star formation. This caused the appearance of overdensi…
Resolving white dwarf binaries within globular clusters with LISA
Radboud University（拉德堡德大学）；Leiden University（莱顿大学）；University of Auckland（奥克兰大学）；SRON, Netherlands Institute for Space Research（荷兰空间研究所（SRON））；KU Leuven（荷语鲁汶大学）；Institute of High Energy Physics, Chinese Academy of Sciences（中国科学院高能物理研究所）；University of Chinese Academy of Sciences（中国科学院大学）
Within a 200 pc sphere around the Sun we search for the Hyades tidal tails in the Gaia DR2 dataset. We use a modified convergent point method to search for stars with space velocities close to the space velocity of the Hyades cluster. We find a clear indication for the existence of the Hyades tidal tails, a preceding tail extending up to 170 pc from the centre of the Hyades with 292 stars (36 contaminants), and a following tail up to 70 pc with 237 stars (32 contaminants). A comparison with an N-body model of the cluster and its tails shows remarkably good coincidence. Five white dwarfs are fo…
